Iain McNeill said:
Indeed it would be useful!
When I tested the input, I did use pin 1. But alas, no sound.
I too noticed that "CTRL" on the orange and wonder if it's an activation lead of some sort.... Hmmm..... From CTRL to GRND I'm getting 65V, whereas the V+ and V- are +67.7V and -67.7V respectively.
EDIT: since the unit had been controlled by a digital volume knob, could this be the source of the level control? Now that the preamp section is out of action could this be our issue?
Re: Changed mission? AMP SALVAGE
See: http://www.diyaudio.com/forums/showthread.php?s=&threadid=145521
I'm having a little difficulty -- partly cold feet and also limited knowledge of this stuff.
That almost what I'm trying to do with my B&K AVR307, except that this receiver works perfectly but I want to turn it into a 7-channel power amp.ZepOfLed said:
See: http://www.diyaudio.com/forums/showthread.php?s=&threadid=145521
I'm having a little difficulty -- partly cold feet and also limited knowledge of this stuff.
Similar goals!
Hey MTA!
My friend has a 307
I'm fairly certain that you and I are correct in that the blue/green wires are where the signal inputs, where blue is the signal and green is a ground.
As far as getting the amp to work without the processing boards.... this is where I'm stuck. I'm sure that your power supply and amp modules are very similar to mine (though probably not the same). If one of us figures out how to do circumvent this issue, I'm sure the other may benefit from the knowledge.
You can see where the rails connect to the amp modules via the red, black, and orange wires. The red and black are V+ and V- respectively and the orange is this "CTRL" wire. I'm not sure what this is exactly, but I have a feeling that it enables the amp to function. My theory is that the orange wire was controlled by a function on one of the processing boards, enabling and disabling the amp as necessary (perhaps even controlling the level?). I'm really stuck here, but I'm certain that the key lies with this mysterious "CTRL" wire. If you get anywhere with this on your project, be sure to let me know! I will certainly do the same. Cheers!
BTW: why would you want to risk damaging such a perfectly good receiver? I know how good it sounds already! If money is no object or you have another one to take its place then I might understand. All I know is, at this point with the level of skill and knowledge I have on this subject (very minimal), I would be very worried about screwing something up. You might be above me though, good luck!
Hey MTA!
My friend has a 307
I'm fairly certain that you and I are correct in that the blue/green wires are where the signal inputs, where blue is the signal and green is a ground.
As far as getting the amp to work without the processing boards.... this is where I'm stuck. I'm sure that your power supply and amp modules are very similar to mine (though probably not the same). If one of us figures out how to do circumvent this issue, I'm sure the other may benefit from the knowledge.
You can see where the rails connect to the amp modules via the red, black, and orange wires. The red and black are V+ and V- respectively and the orange is this "CTRL" wire. I'm not sure what this is exactly, but I have a feeling that it enables the amp to function. My theory is that the orange wire was controlled by a function on one of the processing boards, enabling and disabling the amp as necessary (perhaps even controlling the level?). I'm really stuck here, but I'm certain that the key lies with this mysterious "CTRL" wire. If you get anywhere with this on your project, be sure to let me know! I will certainly do the same. Cheers!
BTW: why would you want to risk damaging such a perfectly good receiver? I know how good it sounds already! If money is no object or you have another one to take its place then I might understand. All I know is, at this point with the level of skill and knowledge I have on this subject (very minimal), I would be very worried about screwing something up. You might be above me though, good luck!
Schematic? Yes please!
MTA,
I would surely like to have that schematic if you don't mind.
I'm sure that the similarities between the units will be helpful in some way.
I tried to PM, but I couldn't find out how....
Anyway, if you could send it to my email, zepofled@gmail.com I would be very grateful indeed!
MTA,
I would surely like to have that schematic if you don't mind
.I'm sure that the similarities between the units will be helpful in some way.
I tried to PM, but I couldn't find out how....
Anyway, if you could send it to my email, zepofled@gmail.com I would be very grateful indeed!
Ok Zep, I emailed you the schematic.
BTW, before I bought the 307 (used) I owned a 202, which I loved. The only reason I sold the 202 was because I wanted 7-channel. Both have impressive amp sections but have dated video sections because all serious AV now really depend upon HDMI inputs which they lack.
My plan is to convert the 307 into a 7-channel power amp. You seem to know more about this than me, so if you can crack this nut, I'd sure appreciate some technical help.
BTW, before I bought the 307 (used) I owned a 202, which I loved. The only reason I sold the 202 was because I wanted 7-channel. Both have impressive amp sections but have dated video sections because all serious AV now really depend upon HDMI inputs which they lack.
My plan is to convert the 307 into a 7-channel power amp. You seem to know more about this than me, so if you can crack this nut, I'd sure appreciate some technical help.
Thanks MTA,
I'll be collaborating with you on your own thread as well as here with Iain and whoever else, so hopefully things won't get too confusing .
I do see the orange "CTRL" wires in the schematics, but I can't tell from those alone what they're for (maybe someone else can?). Hopefully your testing will yeild some useful results.
Anyone who thinks they might be able to help identify the purpose of this "CTRL" wire and wants to see the schematic, just contact MTA or myself.
I'll be collaborating with you on your own thread as well as here with Iain and whoever else, so hopefully things won't get too confusing
.I do see the orange "CTRL" wires in the schematics, but I can't tell from those alone what they're for (maybe someone else can?). Hopefully your testing will yeild some useful results.
Anyone who thinks they might be able to help identify the purpose of this "CTRL" wire and wants to see the schematic, just contact MTA or myself.
CTRL line = AMP enabler
After taking a look at the avr-307 schematic that MTA provided, I'm sure that the orange CTRL wires leading from the power supply to the amp modules are amp enabler leads. I followed them all the way back (with help from the schematics) to the motherboard where it originates in the XILINX SPARTAN logic chip. It starts as "CTRL" on the amps and then goes by the names "Amp_en" and "AON" along the path back to the chip. I'm not sure how this mechanism works exactly, but I need to fool the amp modules into thinking that they are receiving the enabling signal from the CTRL leads. Where do I even start if I want to find out more? I'm hoping that MTA's tests may tell us something... Without this signal telling the amp to activate, it appears to remain inactive, and completely useless.
2 options as I see it:
1. fool the amp by making an idential Amp enabler signal
2. disable and circumvent the control circuit, leaving the amp in an "always on" state
Any ideas?
After taking a look at the avr-307 schematic that MTA provided, I'm sure that the orange CTRL wires leading from the power supply to the amp modules are amp enabler leads. I followed them all the way back (with help from the schematics) to the motherboard where it originates in the XILINX SPARTAN logic chip. It starts as "CTRL" on the amps and then goes by the names "Amp_en" and "AON" along the path back to the chip. I'm not sure how this mechanism works exactly, but I need to fool the amp modules into thinking that they are receiving the enabling signal from the CTRL leads. Where do I even start if I want to find out more? I'm hoping that MTA's tests may tell us something... Without this signal telling the amp to activate, it appears to remain inactive, and completely useless.
2 options as I see it:
1. fool the amp by making an idential Amp enabler signal
2. disable and circumvent the control circuit, leaving the amp in an "always on" state
Any ideas?
Schematics are your friend
Yes, the CTRL turns on the amp channel by turning on the driver chain bias.
Tie the CTRL line to ground. This turns on Q13 which turns on Q6 which turns off Q7 which allows Q5&Q8 to bias up the input and driver stages.
Input is on pin 5 (pin 1 as I called it by mistake) pin 1 seems to go to channel 2. Anyway, you should be able to verify that the input pin because it has a trace that goes to the electrolytic cap C13 -ve pin. It's single ended input so you can tie audio ground to amp ground at the connector.(pin 4 - check with ohmmeter)
power her up and you should be in business.
I'd solder wires or 2nd connectors to the backside of the connectors if you can't find matching housings & crimps. That way they won't be damaged. Digikey has an excellent selection but it's hard to match up exactly.
If you get a power on pop then you may need to have a delay circuit on the CTLR connection to ground - or a separate switch. Let's worry about that later.
edit: I see you can permanently enable the channel by shorting R30
Yes, the CTRL turns on the amp channel by turning on the driver chain bias.
Tie the CTRL line to ground. This turns on Q13 which turns on Q6 which turns off Q7 which allows Q5&Q8 to bias up the input and driver stages.
Input is on pin 5 (pin 1 as I called it by mistake) pin 1 seems to go to channel 2. Anyway, you should be able to verify that the input pin because it has a trace that goes to the electrolytic cap C13 -ve pin. It's single ended input so you can tie audio ground to amp ground at the connector.(pin 4 - check with ohmmeter)
power her up and you should be in business.
I'd solder wires or 2nd connectors to the backside of the connectors if you can't find matching housings & crimps. That way they won't be damaged. Digikey has an excellent selection but it's hard to match up exactly.
If you get a power on pop then you may need to have a delay circuit on the CTLR connection to ground - or a separate switch. Let's worry about that later.
edit: I see you can permanently enable the channel by shorting R30
My 307 has had the cover off and sitting on my coffee table in the den waiting for me to figure out how to precede. Iain, you make it sound easy. Too bad I haven't digested all of what you wrote.
So I ask, is what Zep and I plan to do, namely bypass the pre-amp section of his AVR202i and my AVR307, respectively, and end up with effectively power amps, as easy as you make it sound?
There are some hitches (I think.) I'd want to avoid clipping wires on the Molex connectors to allow for an "undo scenario." However, that requires the hard prospect of finding matching-mated gender connectors. In addition, the inputs on the back are on circuit boards. Several boards needs to be pulled away (not even disconnected, since those go to the pre-amp section) and replaced with five (or seven, in the case of the 307) RCA inputs.
Apart from acquiring the schematic, I've even procured the same green and blue wire that B&K used from Spectrum Cable Corp. of Rochester, N.Y.
So I ask, is what Zep and I plan to do, namely bypass the pre-amp section of his AVR202i and my AVR307, respectively, and end up with effectively power amps, as easy as you make it sound?
There are some hitches (I think.) I'd want to avoid clipping wires on the Molex connectors to allow for an "undo scenario." However, that requires the hard prospect of finding matching-mated gender connectors. In addition, the inputs on the back are on circuit boards. Several boards needs to be pulled away (not even disconnected, since those go to the pre-amp section) and replaced with five (or seven, in the case of the 307) RCA inputs.
Apart from acquiring the schematic, I've even procured the same green and blue wire that B&K used from Spectrum Cable Corp. of Rochester, N.Y.
Thanks Iain,
I attempted to do as you said. All I get at the speaker, however, is a signal that is only as strong as the input signal. I tested this by running the RCA through the amp to the speaker, and then directly to the speaker. They were roughly the same level (very very low). I'm not sure what could be causing this. Any thoughts?
I attempted to do as you said. All I get at the speaker, however, is a signal that is only as strong as the input signal. I tested this by running the RCA through the amp to the speaker, and then directly to the speaker. They were roughly the same level (very very low). I'm not sure what could be causing this. Any thoughts?
Personally, I'd take the boards that I want to use (PSU & amp boards) and mount them in a different chassis. This can be done without modifying the boards so that they can be rebuilt at a later date.
This allows more space to work and gets rid of wasteful power consumption on unneeded DSP, video, display etcetc.
Alternatively, you could just disconnect the 5 pin connectors from the amp board and solder shielded cable onto the backs of the connectors as I described and bring the amp inputs out to a chassis add-on plate with the new RCA's.
There may be some hum issues to resolve to fix the grounding but this shouldn't be too hard.
Regarding grounding:
Zep: I see there are 2 ground symbols on the schematic. If you are using the boards removed from the rest of the system, you may need to tie the two grounds. This may be as simple as adding a wire from the signal input on the amp board back to the star point at the PSU.
Looking at the feedback network, this thing should have a gain of 30 or so.
This allows more space to work and gets rid of wasteful power consumption on unneeded DSP, video, display etcetc.
Alternatively, you could just disconnect the 5 pin connectors from the amp board and solder shielded cable onto the backs of the connectors as I described and bring the amp inputs out to a chassis add-on plate with the new RCA's.
There may be some hum issues to resolve to fix the grounding but this shouldn't be too hard.
Regarding grounding:
Zep: I see there are 2 ground symbols on the schematic. If you are using the boards removed from the rest of the system, you may need to tie the two grounds. This may be as simple as adding a wire from the signal input on the amp board back to the star point at the PSU.
Looking at the feedback network, this thing should have a gain of 30 or so.
2 amp modules ruined?
Ok, I feel like such an idiot...
I don't know what happened, but I must have shorted something in my tinkering... With only the PSU and amp boards connected (CTRL NOT attached to ground), I get around 40V across the speaker terminals. When CTRL is NOT grounded, the amp should be deactivated... Something is clearly wrong. This is only on the board with two channels. The board with three channels reads almost 0V across the speaker terminals, which I expect. AHHHH! I read an article about learning how to build amps, and it said "you WILL blow up components along the way." I was hoping to postpone that for a little while longer....
I don't know how to go about testing components since the board is attached to the heatsink. I removed the hex screws that hold the MOSFETs to the heatsink, but apparently there is also some sort of adhesive. This is preventing me from accessing the back of the board to test terminals.
I will still continue my work on this project, even if it's only for 3 channels, but I would really like to have all 5. Any suggestions?
Ok, I feel like such an idiot...
I don't know what happened, but I must have shorted something in my tinkering... With only the PSU and amp boards connected (CTRL NOT attached to ground), I get around 40V across the speaker terminals. When CTRL is NOT grounded, the amp should be deactivated... Something is clearly wrong. This is only on the board with two channels. The board with three channels reads almost 0V across the speaker terminals, which I expect. AHHHH! I read an article about learning how to build amps, and it said "you WILL blow up components along the way." I was hoping to postpone that for a little while longer....
I don't know how to go about testing components since the board is attached to the heatsink. I removed the hex screws that hold the MOSFETs to the heatsink, but apparently there is also some sort of adhesive. This is preventing me from accessing the back of the board to test terminals.
I will still continue my work on this project, even if it's only for 3 channels, but I would really like to have all 5. Any suggestions?
Are these the same two channels that were putting out a small signal two posts ago? I hope you weren't testing the amps into your very expensive speakers?! A cheap 5-10ohm resistor of several watts capability is a much better starting point.
When you measured 40V on the output, was there any load? Powering up the stage could be enough to inject a little charge into an unloaded output to charge it to 40V. Your meter with it's 100'sKohms resistance won't discharge this. However, when you ground CTRL it should drop to zero. You should operate with a load in the 5-10ohm range tho.
The adhesive holding the o/p trannies to the heatsink is only heatsink compound to get a good thermal contact. It's stiff & gooey when cold but should peel apart. You'll need to redistribute before reassembly or reapply fresh if you clean it off.
When you measured 40V on the output, was there any load? Powering up the stage could be enough to inject a little charge into an unloaded output to charge it to 40V. Your meter with it's 100'sKohms resistance won't discharge this. However, when you ground CTRL it should drop to zero. You should operate with a load in the 5-10ohm range tho.
The adhesive holding the o/p trannies to the heatsink is only heatsink compound to get a good thermal contact. It's stiff & gooey when cold but should peel apart. You'll need to redistribute before reassembly or reapply fresh if you clean it off.
Here's my new situation.
With only the PSU and amp modules connected:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*No inputs connected (but grounded), CTRL not grounded
-The board with three modules sends about 0.02V DC to the speaker terminals.
-The board with two modules sends about 40V DC to the speaker terminals.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*No inputs connected (but grounded), CTRL grounded
-The board with three modules sends no potential (0V) to the speaker terminals.
-The board with two modules sends about 35V DC to the speaker terminals.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
These results make be believe that something got shorted, though I don't know what. Where should I start looking?
BTW:
With only the PSU and amp modules connected:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*No inputs connected (but grounded), CTRL not grounded
-The board with three modules sends about 0.02V DC to the speaker terminals.
-The board with two modules sends about 40V DC to the speaker terminals.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*No inputs connected (but grounded), CTRL grounded
-The board with three modules sends no potential (0V) to the speaker terminals.
-The board with two modules sends about 35V DC to the speaker terminals.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
These results make be believe that something got shorted, though I don't know what. Where should I start looking?
BTW:
I didn't use any of my good speakers, but I did hook up a crappy plastic sony speaker that goes to an old cd/stereo combo. At some point yesterday it did get blown, as I can smell the burning and it crackles. I'm not really prepared to do this type of work, and so I don't have any spare electronics parts lying around. I'll work on getting a 5-10 ohm resistor (high wattage) to test with, but until then I guess I can just use the blown sony. It still plays, if a bit crackly (and I don't really care about it).
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